Current differentiated timing mechanism for the purpose of tripping circuit breakers or switches



y 1943 B o. WATKINS I 2,319,279

CURRENT DIFFERENTIATEI) TIMING MECHANISM FOR THE PURPOSE OF TRIPPING CIRCUIT BREAKERS 0R SWITCHES Filed Aug. 29, 1941 6 4 T3 T2 T1 Patented May 18, 1943 2,319,279 CURRENT DIFFERENTIATED TIMING MECH- ANISM FOR THE PURPOSE OF TRIPPING CIRCUIT BREAKERS R SWITCHES Bruce 0. Watkins, Tucson, Ariz. Application August 29, 1941, Serial No. 408,731

I 4 Claims. (01. 20o 97) (Granted under the act of March 3, 1883, 9'

amended April 30, I92

The invention described herein may be manu factured and used by or for the Government of the United States for governmental purposes without the payment to me of any royalty thereon, in accordance with the provisions of the act of April 30, 1928 (ch. 460. 45 Stat. L. 467).

My invention relates to a current diiferentiated timing mechanism for the purpose of tripping a circuit breaker or switch and is applicable primarily to lines supplying power. wherein it is desired to cut off the. current within a definite period after the current exceeds a predetermined value.

In the drawing in which like reference characters designate like parts,

Fig. 1 is an ele ational view partly in section of my timing mechanism,

2 is an elevational view at right angles to that of Fig. 1,

Fig. 3 is a schematic view of a modification of I the structure illustrated in Figs. 1 and 2,

Fig. 4 diagrammatically illustrates a plurality of circuit breakers, or switches provided with my invention, connected in a series system, and

Fig. 5diagrammatically illustrates my invention as applied to a single circuit breaker, or automatic switch.

In Figs. 1 and 2 I have illustrated a case I the back 2 of which supports a bracket 3, on the under side of which is mounted a solenoid winding 4, the form 5 of which supports a casing 6 which with the bracket 3 forms bearings forthe solenoid core mechanism I.

This mechanism includes a shaft 8, the reruced portion 9 of which carries a sliding armature IIJ having one conical end I I for purposes to be hereinafter described.

Around that portion of the shaft 8 which ex- -tends below the casing 6 I provide a compression spring l2 which, positioned between the casing 8 and the flanged end I3 of the shaft 8, moves the core mechanism I to the position illustrated when no current flows in the solenoid winding 4.

At the opposite end of the shaft 8 I provide a sliding joint in the nature of a dash-pot structure I4 carrying a rack I5 which engages the pinion I6 mounted on a shaft I! mounted in bearings I8 in a support I9 mounted on the back 2 of the case I. This nature of the joint I4 is such that it can transmit tension only.

The shaft I1 is driven by a spring 20, the speed of rotation of the shaft being controlled by a fly-wheel 2i or other suitable mechanism.

In the several figures I have illustrated this flywheel as a cam for operating the pin coupling 22 for actuating the trip mechanism of a circuit breaker or automatic switch, when connected in the manner diagrammatically iilustrated in Fig. 5.

The solenoid winding t, the armature I0 and the spring I 2 are designed in such a. manner that when the winding 4 is connected in series in a line 23 containing a. circuit breaker or automatic switch 24 a current of predetermined value will flow in the line without actuating the armature III. When the current increases above this value the armature II drives the shaft 8 upward until the spring pressed latch 25 engages in the detent 26 in the shaft 8. The spring 2. then starts the fly-wheel 2| and depending upon the relative inertia of the fly-wheel and the sprin a predetermined interval of time elapses before the wheel 27 of the coupling 22 drops in the recess 28 of the fly-wheel, thus tripping the circuit breaker. When current flow through the solenoid coil stops, the armature III drops back on the shaft 8, the conical en'd forcing the latch 25 out of the detent 26 permitting the spring I2 to return the elements to the'position illustrated.

In Fig. 3 I have shown the elements in horizontal position with the armature III fixed on the shaft 8 and a magnetic latch 25 in lieu of the spring pressed latch of Figs. 1 and 2.

In each of the structures, once a predeter mined value of current is exceeded the time required to trip the circuit breaker or switch is independent of the current, on the setting of the timing mechanism.

This principle makes it possible to use a large number of circuit breakers in series on a given system as lilustrated in Fig. 4, wherein, for example, the timing mechanisms Ti, T2, T3 in block A, remote from the power source, are set to start operation at 20 amperes current, timing mechanisms T4, T5, T6 in block B, less remote from the power source, at amperes current, and timing mechanisms T7, T3, T9 in block C, still less remote from the power source, at amperes current,

and the timing mechanism 'set so that the cir-' cuit breakers actuated by timing mechanisms T1, T4 and T; will trip out in 0.2 sec.; T2, T5 and Ta in 0.4 sec.; and T3, T6 and T9 in 0.6 sec. In this manner should the fault current occur at a point remote from the power source, the value of the fault current determines which circuit breakers of the several banks are tripped out. After the current ceases to flow the circuit'breakers automatically reset out to the one nearest the source of trouble.

The circuit breakers T1, T2, eta, indicated in and dependent only greater than nY groups A, B and C in Fig. 4, are tripped by controlling mechanism such as is shown in Fig. 1. The mechanisms controlling breakers T1, Ta and T3 (group A, Fig. 4) have a coil 4 of a certain rating, which, for example, may be X amperes, while the mechanisms controling the circuit breakers T1, T5 and T6 (group B, Fig. 4) have a coil rating of Y amperes which is greater than X amperes, and the circuit breakers T1, Ta and To (group C, Fig. 4) have a coil rating of Z amperes which is greater than Y amper'es. The coil 4 and its armature I are so proportioned that the coil raises the armature and starts the mechanism on any current greater than 'n times the rating, where n is any desired figure greater than the integer 1. Thus the mechanisms for the circuit breakers T1, T2 and T3 in group A will start operating on a current greater than 121! amperes, While those for the circuit breakers T4, T and To in group B will start operating on a, current amperes and those for the circuit breakers T1, T5 and T9 in group C will start operating on a current greater than 11.2 amperes.

Since the amount of current in a short circuit on any radial electric system decreases as the distance from the power source increases, the coil ratings in each group A, B and down from source to end.

Assuming that a short circuit occurs on a system on the load side of breaker T1, and that the short circuit current is greater than nX amperes, but less .than nY amperes or nZ amperes, the three timing mechanisms controlled by circuit breakers T1, T2 and T: will start simultaneously.

However, the setting of the spring 20 in -the. support IQ is set for a certain time, for instance 0.2 second on the mechanism for circuit breaker T1, while for the circuit breaker T2, the mechanism is set for a greater time for instance 0.3 second, and for the circuit breaker T3 the mechanism is for a longer time for instance.0.4 second. Thus, rotation of the fly-wheel 2| brings its notch 28 under the roller 21, after (l.2 second for the mechanism for the circuit breaker T1. Since the mechanisms for the circuit breakers T2 and T3 are adjusted for a longer time they are recycled before tripping their respective circuit breakers by the spring H as soon as the short circuit is removed by the circuit breaker T1.

' This disconnects the line beyond circuit breaker T1, but all other lines remain energized, and since the short circuit current was less thanJtY 01' n2 amperes, the mechanisms for the circuit breakers T4 to T9 in groups B and C did not operate.

If there is a, short circuit on the line between C are stepped smears mechanism, the combination of a rotatable cam adapted in one position to actuate said trip-out mechanism, a spring adapted to rotate said cam from a position remote from said actuating position to said actuating position at a predetermined rate of acceleration, a second spring more powerful than the first adapted to rotate said cam from said actuating position to said remote position and electro-mechanical means for overpowering said second spring and permitting said first named spring to rotate said cam at its predetermined rate of acceleration.

2. In a delay mechanism for tripping out-circuit breakers and the like having a trip-out mechanism, the combination of a rotatable cam adapted in one position to actuate said trip-out mechanism, a spring adapted to rotate said cam from a position remote from said actuating posi-' tion to said actuating position at a. predetermined rate of acceleration, means for rotating said cam from said actuating position to said remote position comprising pinion attached to said cam, a rack in engagement with said pinion, a shaft arranged in the plane of said pinion, a spring for urging said shaft away from said pinion and a joint between said rack and said shaft transmitting tension only, and a solenoid, the armature of which is attached iosaid shaft and adapted to drive said shaft toward said pinion upon a predetermined current flow in the coil permitting said first named of said solenoid and spring to rotate said cam at its predetermined rate of acceleration.

3. In a delay mechamsm for tripping-out circuit breakers and the like having a trip-out mechanism, the combination of a rotatable cam adapted in one positionto actuate said trip-out mechanism, a coil spring adapted to rotate said cam from a position remote from said actuating position to said actuating position at a predetermined rate of acceleration, a pinion attached to said cam, a rack in engagement with said pinion,

- a shaft connected to said rack by means of a pressed position and circuit breakers of group'A and those of group B, the group B mechanism coils 4 would be adjusted so that the trip would occur on nY amperes, which would be short circuit current between cijrcuit breakers T3 and T4. The timin for the mechanism for T4 circuit breaker would be set, for instance, for 0.2 second; that for T5 circuit breaker for 0.3 second, andthat for circuit breaker T6 for 0.4 second, as for the circuit breakers in Group A. Qn a line fault between circuit breakers T3 and T1 operation similar to that just describedabove will occur.

Having thus described my inventiom what I claim is:

1. In a delay mechanism for tripping-out circuit breakers and the like having a trip-out tion through said joint transmitting tension only, a compression spring more powerful than the coil spring engaging said shaft and adapted to rotate said cam from said actuating position to said remote posijoint, rack and pinion, and a solenoid, the armature of which engages said shaft for compressing said compression spring and relieving said joint of any tension and means for locking said compression spring in its compermitting said coil spring to rotate said cam at its predetermined rate of acceleration.

4. In a delay mechanism for tripping-out circuit breakers and the like having a trip-out mechanism, the combination of a solenoid winding adapted to be connected in series with said circuit breaker, an armature within'said solenoid adapted to be driven in one direction by current flow through said winding, a shaft connected to said armature, a spring at one end of said shaft for urging the shaft in a direction opposing movement by said armature, a, timing mechanism, means at the other end of said shaft for starting said timing mechanism and means actuated by said-timing mechanism after a 'predeter-' mined lapse of time for actuatingthe trip-out or said circuit breaker.

' BRUCE O. WATKINS. 

